1. Field of the Invention
The present invention relates to an alternator for use in an automotive vehicle.
2. Description of Related Art
An automotive alternator having a minus rectifier element, a base portion of which extends toward a rear frame and contacts the rear frame for better dissipating heat, has been known hitherto. An example of such an alternator is disclosed in JP-A-2002-519987. In this alternator, a plus cooling fin on which plus rectifier elements are mounted and a minus cooling fin on which minus rectifier elements are amounted are connected to a rear frame, forming a two-story structure. A base portion of each minus rectifier element extends from the minus cooling fin toward the rear frame and contacts the rear frame, thereby to better cool the minus rectifier element. Since the plus rectifier elements are positioned at a place better cooled by cooing air in this structure, it is not necessary for the plus rectifier elements to devise a structure for better cooling.
In the rectifier cooling structure mentioned above, the following problems are involved. (1) It is very difficult to establish a close contact between a base portion of the minus rectifier element and a seat portion of the rear frame for all of the minus rectifier elements. This is because a length of the base portion extending from the fin cannot be made uniform for all minus rectifier elements since the minus rectifier element is forcibly inserted into a hole of the minus cooling fin. If there is a minus rectifier element not contacting the rear frame, that element is not sufficiently cooled and may be damaged by heat. (2) If it is tried to establish the contact with the rear frame for all of the minus rectifier elements, some of the rectifier elements may be pushed against the rear frame with a force unbearable by the rectifier element. (3) In order to establish the close contact between the minus rectifier element and the rear frame for all of them, the length of the base portion extending from the minus cooling fin has to be very precisely controlled for all of the minus rectifier elements. This requires an impermissibly high manufacturing cost.